The present invention relates generally to antennas. More particularly, the present invention relates to antennas having a low profile for use in roadways, sewer manholes, and other applications where a low profile is desirable.
The collection of data from sanitary or storm sewer networks and other underground or enclosed systems has become increasingly common and useful. For example, in an underground sewer network, flow monitors may be used to collect data such as depth, volume, velocity, and/or other measurable parameters in a certain location. When such monitors are used, it is often desirable to collect the data in a central location, such as a remote computer or data collection system, so that data from multiple monitors can be analyzed, stored, processed, compared, and/or presented to a user. Because of the impracticality of connecting monitors that may be located throughout such a sewer or other network to a central processor via direct wiring, it is desirable that such monitors transmit their data to a remote computer through a wireless communications medium.
The application of wireless technology to transmit and/or receive data from and/or deliver data to flow monitors requires a suitable antenna for reception and/or transmission. For example, sewer flow monitors are typically installed within a sewer network inside or near manholes in order to provide access for installation, maintenance, and repair. Thus, the monitor may communicate with a remote unit via a wireless transmitter that is also located near or within the manhole. However, if transmitter""s antenna is mounted so that the antenna is below the manhole""s cover, substantial losses in signal strength, such as RF energy losses, will result from factors such as signal attenuation and the fact that the antenna is mounted below the ground plane.
One solution to this problem is to mount the antenna above the ground, outside of the manhole. However, conventional antennas normally require a mast or pole type of mounting. Thus, conventional antennas have an elevation that renders them undesirable for use in many locations, such as roadways and sidewalks where vehicular and/or pedestrian traffic will flow. Thus, a shorter, or low profile, antenna is desirable in such a location.
Existing low profile antennas still require a substantial elevation above the ground surface. Examples of such antennas may be found in U.S. Pat. No. 5,877,703, to Bloss et al. Such antennas are subject to abuse from, and may be damaged by, roadway traffic, such as cars, trucks, buses, and other vehicles, as the traffic drives over them, directly placing substantial loads on the antenna. Other roadway vehicles such as snowplows can cause even more damage to an antenna that is raised above the roadway. In addition, such antennas require modification to the manhole cover, such as the drilling of a hole, to connect the above-ground antenna to the underground flow meter. Such holes are generally large, as they are also used as a means to secure the antenna to the manhole and/or to connect the antenna to equipment below the manhole cover.
Accordingly, it is desirable to provide an improved low profile antenna as disclosed herein.
It is therefore an object of the present invention to provide an improved low profile antenna.
It is an additional object of the present invention to provide an antenna having a profile that reduces or eliminates the susceptibility for damage of the antenna resulting from roadway traffic.
In accordance with a preferred embodiment of the present invention, a low profile antenna for receiving and/or transmitting radio frequencies includes a first elongated element made from an electrically conductive material, a second elongated element made from the electrically conductive material, and a cable that is conductively attached to the first and second elongated elements. The first and second elongated elements each have a height that is of a low profile and lengths that are substantially equal. The elongated elements are covered at least partially with a substantially non-conductive covering.
Optionally and preferably, the first elongated element and the second elongated element are positioned to extend in opposite directions, form substantially a straight line, and are separated by a gap to provide a dipole antenna. Also optionally, the first elongated element and the second elongated element are sized and positioned to fit within one or more grooves or recesses of a standard manhole cover.
In accordance with the above-described embodiment, the electrically conductive material preferably includes copper. The height that is of a low profile is preferably about one-fourth of an inch or less, and the optional substantially straight line formed by the first and second elements has a length that corresponds to an operating frequency band of the antenna. The length preferably provides an electrically tuned antenna that is capable of transmission in close proximity to a surface.
As additional options, the cable has a diameter that is at least as small as the diameter of a standard manhole cover opening, and the substantially non-conductive covering is comprised of at least one of rubber, plastic, non-metallic tubing, an adhesive, and a non-metallic substrate. The cable may also be connected to a transmitter and/or a receiver. Optionally, the antenna includes an adhesive material that is affixed to at least a portion of the substantially non-conductive covering. Also optionally, the elongated elements may be positioned within at least one groove or recess of a standard manhole cover, or they may be embedded within or flush with a traffic surface.
In accordance with an alternate embodiment, a method of installing an antenna in a low profile position includes the steps of locating a low profile dipole antenna in a position that is substantially flush with or embedded within a traffic surface, placing a cable having a first end and a second end so that the first end is conductively attached to the antenna, the second end is attached to at least one of a transmitter and a receiver located in a system under the traffic surface, and a portion of the cable located between the ends enters the system through an opening, coating the antenna with a substantially non-conductive covering, and substantially sealing the opening with a sealant.
Optionally, in this method, the position that is substantially flush with the traffic surface is about one-fourth of an inch or less. The non-conductive covering is optionally and preferably is comprised of at least one of rubber, plastic, non-metallic tubing, an adhesive, and a non-metallic substrate. Optionally and preferably, the dipole antenna includes two elongated elements having substantially equal lengths positioned to extend on opposite directions from a point, and the first end of the cable is attached to the elements at the point. Also optionally and preferably, the traffic surface is at least one of a manhole cover, a road, and a sidewalk, and the opening is a standard manhole cover opening, a storm sewer grate, or another opening that is substantially at or near ground level.
There have thus been outlined the more important features of the invention in order that the detailed description thereof that follows may be better understood, and in order that the present contribution to the art may be better appreciated. There are, of course, additional features of the invention that will be described below and which will form at least part of the subject matter of the claims appended hereto.
In this respect, before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and to the arrangements of the components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced and carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein, as well as the abstract included below, are for the purpose of description and should not be regarded as limiting in any way.
As such, those skilled in the art will appreciate that the concept and objectives, upon which this disclosure is based, may be readily used as a basis for the designing of other structures, methods and systems for carrying out the several purposes of the present invention. It is important, therefore, that the claims be regarded as including such equivalent constructions insofar as they do not depart from the spirit and scope of the present invention.